26 January 2010

by Bill Cooke

The 3.2L EBDI engine. Click to enlarge.

Engineering firm Ricardo and Growth Energy, a trade association promoting the use of ethanol fuel, are collaborating on two demonstrator vehicles incorporating Ricardo’s Ethanol Boosted Direct Injection (EBDI) engine technology (earlier post) showing that even for larger vehicles extreme optimization of ethanol combustion can enable engine downsizing of the order of 50% and still deliver substantial fuel economy and CO2 emission improvements from a cost-effective, high performance, inherently low emission powertrain.

Based on test work already carried out, Ricardo estimates that a fuel economy improvement of up to 30% is possible with no loss of power or performance, using a downsized EBDI engine in place of currently available gasoline powertrain technology. For the demonstrators, Ricardo plans to modify two GM Sierra 3500 HD heavy-duty pickup trucks and replace a base 6-liter gasoline V-8 in one with the heavily boosted 3.2-liter EBDI engine—resulting in up to a 16.8% fuel economy improvement. Ricardo is replacing a 6.6-liter turbo diesel V-8 in the other.

One of the trucks. Click to enlarge.

For heavy-duty trucks engine torque is a key performance metric and Ricardo expects the EBDI engine to offer 1.5x the torque of the gasoline engine and match the torque of the 6.6L turbo diesel engine while weighing 400 to 500 pounds less than the diesel.

Following completion of the 10-month project, the demonstrator vehicles will be available for a range of demonstration, test and evaluation exercises to be organized by Growth Energy and Ricardo.

In the past, when people have created flex fuel engines they have taken the gasoline engine and converted it to burn varying degrees of ethanol. Since ethanol has only two thirds of the energy content of gasoline on a per gallon basis, fuel economy has suffered leading to customer dissatisfaction, but ethanol also has some inherent advantages such as high-octane and a higher heat of vaporization and by applying several cutting edge technologies Ricardo has been able to harness the full capabilities of ethanol to create an engine that gets high fuel economy with a domestically produced renewable fuel.

—Kent Niederhofer, President of Ricardo

In volume production, the engine is expected to retail for $4,000 to $4,500 more than the base gasoline engine or approximately half the premium associated with a diesel engine. The diesel premium is expected to grow to $9,500 by 2013 in order to comply with more stringent air pollution standards. The EBDI’s price premium versus today’s gasoline engine would be offset by fuel economy savings over the life of the vehicle—allowing the owner to get the increased torque performance “for free”. Ricardo expects the EBDI technology to be compatible with existing plans to improve gasoline engines’ pollution performance.

Improving Ethanol’s Cost Performance and Carbon Footprint

The EBDI engine can accommodate ethanol blends ranging from 0 to 85% ethanol (E0 to E85). Ricardo is still collecting data but with an E40 (40% ethanol / 60% gasoline) Ricardo can achieve a mpg that approaches pure gasoline using a fuel with less energy gallon—i.e the E40 blend uses approximately 10% less Btus per mile (6,590 vs 7,260) than gasoline (see table below).

Comparison of different ethanol blend levels in EBDI engine. Click to enlarge.

With today’s economics it would be a financial wash to use the E40 blend verses gasoline but since ethanol and gasoline come from two very different value streams (agriculture vs. petroleum) macro economics may drive significant price differences that the consumer could exploit at a later date. “It will provide consumers with a cost effective choice in fuel, said Rod Beazley, director of the Ricardo Inc. Spark Ignited Engines Product Group.

The most robust way to create various ethanol blends is to have blend pumps that would allow the consumer to choose their level of ethanol. In lieu of a blend pump, the more enterprising consumer could create their own approximate blend by filling up with equal amounts of E0 and E85 each time they refueled.

The customer would be able to tune their torque performance by using blends with more or less ethanol. Using E85, for maximum torque, the driver would have a peak torque of 660 lb-ft (895 N·m) and more than 500 lb-ft (678 N·m) of torque over a 3,600 rpm band (approx 1,400-5,100 rpm). Using E0, the torque would be 14% lower.

As points of comparison, the 6.0-liter gasoline V8 is rated at 353 hp (263 kW) and 373 lb-ft (506 N·m) of torque. The 6.6-liter diesel V-8 is rated at 365 hp (272 kW) and 660 lb-ft (895 N·m) of torque.

The EBDI engine will also improve ethanol’s carbon footprint by requiring less BTUs per mile since, for a given mode of ethanol production, the well to wheel CO2 emissions is directly related to fuel economy.

Development History and Real Horsepower

Ricardo has largely self funded the development of the EBDI engine and appreciates the technical support (parts and engineering) provided by the following companies:

Federal Mogul: Piston, Rod, Bearings, Head Gasket

Behr: Induction System and EGR coolers

Grainger and Worral: Block and Head Castings

Bosch: DI System Hardware

Honeywell: Turbocharger Hardware

Delphi: Ignition System

The original plan was to have testing completed by the end of 2009 but the program had to be put on hold due to the recession. Ricardo is pleased to have Growth Energy's support for the vehicle development phase.

Ricardo has more than 700 hours of testing complete on the development engine and is ready to “take the technology to the streets” by building the two trucks and putting them through various extreme duty cycles. One of the trucks will be a dualie pickup with a fifth wheel trailer mount to prove that the 3.2 L EBDI system can haul up to 16,500 pounds which, according to Niederhofer, is equivalent to “four Clydesdales and a full-size horse trailer.”

Technical Details

We took the stock V-6 and redesigned every component. We are getting diesel-like performance out of an engine that was originally designed to be lightly turbocharged. With our heavy boost we have increased the cylinder pressures to diesel-like levels. We had to work on the bottom end and on the crank and in order to get enough of ethanol into the engine we had to use two fuel pumps. We have an integrated manifold with charge air coolers and EGR coolers help cool down the combustion system. We have two parallel/sequential turbochargers and although our block and heads look unchanged from the outside, inside they are highly modified with structural changes to support the higher cylinder pressures. We also have a high-voltage ignition system to ignite the large amounts of ethanol.

—Rod Beazley

When asked how Ricardo can have different compression ratios for different fuel blends, Luke Cruff, Chief Engineer Gasoline Product Group, replied:

Compression ratio is a function of two things: geometric compression ratio and boosting pressure. The turbochargers and other variable devices can adjust the boosting pressure which allows you to have different effective compression ratios. Diesel engines today run about 17:1 compression ratio which is trending down because the emission regulations while this engine’s compression ratio is closer to 11 to 1.

In addition to the hardware development, Ricardo has significant intellectual property in the algorithms and control software. Niederhofer of Ricardo points out that “a lot of the breakthroughs the team has identified to get this engine to work will find their way into base gasoline engines” independent of ethanol blends. This engine represents an enhancement, not a redirection, of existing trends in automotive powertrains.

Future

Ricardo expects this technology to be used in a variety of markets including agriculture equipment and commercial vehicles but they see automotive as being the lead. The Ricardo team in Europe is pursuing a similar program focusing on much smaller three and four-cylinder engines. Luke Cruff points out:

GM has just recently introduced a 1.4 L turbocharged engine for the Chevy Cruze. We believe that using EBDI technology, you could have a 1.4 L engine power a mid-size car. That would give you approximately the same engine displacement to vehicle weight ratio as the 3.2 L engine in the heavy-duty truck.

Comments

I wonder if this technology could be coupled with FIAT-Chrysler's MULTI-AIR. As is, the technology sounds like something the ethanol community should be jumping for joy over....but there could be even more gains with MULTI-AIR. One of the problems from E85 from the beginning has been less mileage. If plain economics makes this engine more attractive for everyone (businesses, individuals) it could be the new standard for the ICE.

The Automotive Engineering department at Minnesota State University, Mankato has found that a 20 to 30 percent ethanol mixture results in fuel mileage equal or slightly better than straight gasoline, even though total BTUs are less. This was with engines not specifically designed to take advantage of ethanol's higher octane rating.

The boosting is good. Reducing engine weight and losses from pumping and friction are important improvements. However, it's a one-shot and can only yield a relatively small part of the 80% increase we need.

For heavy-duty application in which high engine load is maintained for the majority of the time, the use of alcohol-gasoline blend can reduce the number of fuel injectors.

However, for light trucks and cars that operate the engines in light load for most of the time, the use of a separate alcohol injector can allow for saving in alcohol consumption when the engine load is light. This the MIT Scheme. Henry Gibson would prefer this over the Ricardo-Growth Energy Scheme. Growth Energy would prefer more alcohol consumption, for obvious business reason, although the high use of alcohol is not ecologically sustainable.

Rodger, Rodger.
The MIT approach makes more sense to me, but many think 2 tanks are too complex for the motoring public. I hate to think we are that stupid or lazy, but who knows. Separation adds a lot of good possibilities, but it is a logistical burden all the way along the chain. I would like to see it, the market can sort it out.

@ SJC:
I don't think they are changing the mix at the engine on this one. That would be More efficient, but have penalties mentioned above as well as more ECM inteligence needed.

I am afraid this technology will have too little to offer in the long run and this is why: a Ford Escape hybrid which is basically a box with wheels (very high drag coefficient), it is very heavy (3669 lbs), it has a high compression ratio (12.3) Atkinson engine and it is rated at 34 mpg city/ 31 mpg highway (32.5 mpg combined), still beats my 2007 Toyota Yaris which is only 2346 lbs, has a fairly low drag coefficient, has an Otto cycle engine with a compression ratio of 10.5 and 29 mpg city/35 mpg highway (32 mpg combined).

Ford has not started to used direct injection on the Escape's Atkinson engine but once they do, the compression ratio will easily go north of 15:1. Such high compression ratio, will make the thermal efficiency increase dramatically. An engine with a compression ratio of 15:1 will have an exhaust temperature below 800 degrees Celcius which means a small turbine can be used to convert some of the exhaust into additional electrical energy that can charge a battery. Such low exhaust temperature will eliminate the need of using heat resistant exotic materials to build the turbine.
In short, ethanol boosting will only offer a very small increase of compression ratio to an engine that is already using direct injection.

The $4.5k may be worth it. At 13.7 MPG and 150,000 mile lifetime, the original 6.6 liter will burn ~10,950 gallons of fuel. If we assume that ethanol blends cost the same on a BTU-equivalent scale (BIG assumption), the high-economy mode will use only 74.9% as much energy or ~8200 gallons-equivalent. The savings pay for the engine at well under $2/gal-equivalent.

Freddy;
Not sure this comparison between light vehicles and heavy, make sense. Batteries will not do heavy hauling for over the road distances anytime soon if ever. When comparing compression ratios don't forget the turbo. The article talks about 11:1 but I think this is without boost. With sequencial turbos and sophisticated controls effective compression ratio is anywhere desired in a big efficient envelope.

EBDI is interesting for many reasons, but the name and way its marketed are a clever diversion. The real trick is managing combustion efficiency through healthy use of cooled EGR on a heavily boosted and downsized engine, not through use of Ethanol blended fuels. Nearly all boosted S.I. engines rely heavily on fuel cooling and spark retard to keep the engines from knocking to death or burning up a number of components that are not designed to resist continuous high load operation, ie. pistons, turbine housings & wheels, exhaust manifolds, and catalysts. Because of this, downsized and boosted engines typically get worse fuel economy than a NA engine for a given load point whenever they are running positive manifold pressure. Cooled egr reduces peak combustion temperatures and acts as a knock inhibitor, enabling increased compression ratio, MBT spark timing, and elimination of overfueling. There are other benefits as well but these are the biggies and what make this technology work. Ethanol allows for the EGR rate to be reduced or for the BMEP level to be pumped up but it isn't fundamental to the technology. Its analagous to the impact of running ethanol in a conventional N.A. SI engine. The same is more of less true for D.I.
Many different research houses are developing the same approach and probably SwRI has the most experience. My bet is that we'll see this in production in the next 5 years, but I think the E85 spin is really about marketing for the likes of corn industry and not about technology.

The dual fuel strategy from MIT is very interesting too but I'll save my rant on that one for another day. My main point is that modern diesels are effectively dual fuel given that you have to run DEF, AdBlue, or whatever trademark name you choose in order to meet emissions. If people tolerate this, then why not gas/diesel, gas/ethanol, or diesel/ethanol?

Thanks, UA for your analysis and for pointing out that clean diesel is dual fuel. Indeed, cooled EGR is Ricardo's important trick for boosted gasoline engine.

However, ethanol direct injection provides better charge cooling than gasoline due to the higher heat of vaporization of alcohol, hence reducing the work of compression and more engine net output and efficiency. Since ethanol is a fuel and not a charge diluent, more power and torque can result for a given level of boost in comparison to cooled EGR.

From what I've read; on a light dury vehicle with ethanol boost you'd be refilling the second tank only as often as you refill your windshield washing fluid tank. In fact you could use some brands of windshield washing fluid as an antiknock boost.

There is something valuable about making monsters more efficient as long as those heavy vehicles are really essential and required a high percentage of the time. Otherwise, smaller HEVs like the Ford Vision and Toyota Prius III can move people around with a lot less fuel.

Future common sense size PHEVs will do even much better.

PHEV technology could easily be adapted to larger vehicles and have plenty of torque when both ICE + e-motors are used on an as required basis.